Shift control system for automatic transmission

ABSTRACT

Improved shift control of the present invention is used in an engine driven vehicle having an automatic transmission. Load indicating apparatus responds to the operational load characteristics of the vehicle and produces outputs indicative of variations therein, while a responsively coupled first shift point computing apparatus effects the gear change signal for the transmission when the output indicates a certain load characteristic. A second shift point computer is responsively coupled to the load indicator and provides an output of a gradient operating circuit thereof in order to establish a gear change signal when the output of the load indicating apparatus establishes that a certain load characteristic exists which is co-relative to a gradient exceeding a selected amount.

-[ July 24, 1973 SHIFT CONTROL SYSTEM FOR AUTOMATIC TRANSMISSION [75]Inventors: Eiji Toyoda; Shin Ito; Seitoku Kubo,

all of Toyota, Japan [73] Assignee: Toyota Jidosha Kogyo KabushikiKaisha, Toyota-shi, Japan 22 Filed: Mar. 28, 1972 21 Appl. No.: 238,773

Related U.S. Application Data [63] Continuation-impart of Ser. No.889,062, Dec. 30,

1969, abandoned.

52 U.S. c1. 74/866, 74/752 A 51 Int. Cl. 860k 21/00, Fl6h 57/10 [58]Field of Search 74/866, 752 A, 752 D, 74/731 [56] References CitedUNITED STATES PATENTS 3,122,940 3/1964 Shimwell et al. 74/866 3,267,7628/1966 Reval 74/866 x 3,301,085 1/1967 De Caste] et al. 74/866 2 POWERSOURCE 1c Tl 95 LtJ SHIFT SIGNAL i- A CONTROL 3/1969 Scholl et al.74/866 6/1969 Nelson 74/866 Primary Eagaminer-Arthur T. McKeonAttorney-john WI Malley, GT Lloyd Khig'ht et al.

[57] ABSTRACT Improved shift control of the present invention is used inan engine driven vehicle having an automatic transmission. Loadindicating apparatus responds to the operational load characteristics ofthe vehicle and produces outputs indicative of variations therein, whilea responsively coupled first shift point computing apparatus effects thegear change signal for the transmission when the output indicates acertain load characteristic. A second shift point computer isresponsively coupled to the load indicator and provides an output of agradient operating circuit thereof in order to establish a gear changesignal when the output of the load indicating apparatus establishes thata certain load characteristic exists which is co-relative to a gradientexceeding a selected amount.

36 Claims, 32 Drawing Figures 7' RANSMSS ION HYDRAUL/C C/RCU/T PmmcumzmSHEET 02 0F FIG.

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SHEET 0% OF 19 F/GI 5 H-TESSURE REMAWR VALVE L35 2 -3 SHIFT MEA NS I 2(SH/F7 MEANS I20 MANUAL VALVE PAIENIEB 2 3. 747. 438

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I05 PRESSURE REGULATOR VAL v5 (SH/FT 37 MEANS 2 SH/FT MEA/vs VALVEPATENTED JUL 2 4 I975 SHEET 08 [1F /05 FPESSURE REGULATOR VA L V5 2 3SHIFT MEANS SH/FT MEANS MANUAL VA L V5 PAIENIED JUL 24 I973 3 l [47, 438

SHEET 07 HF 19 /05 PRESSURE REGULATOR VAL V5 35 2- 3 g7 (SH/FT MEANS 2SHIFT MEANS MANUAL VA L VE PAIENTEU Jul 2 4 SHEEI 08 0F /05 PRESSURE RE611.11 TOR VALVE SHIFT ME'A NS SH/Fr MEANS lZO MANUAL VA L V5 PATENTEDJUL24|975 SHEET 09 [1F /05 PRESSURE REGULATOR VALVE SH/Fr lZO MANUALVALVE PAIENIED 3. 747. 438

sum 16 or 19 FIG /9 AMPLITUDE I D/FFER- 329 E/VT/AL 2/7 AMPL/F/Ef? N c47 2/0, 0*" 535 226 REFERENCE AMPL Q) 335 VOLTAGE FIG. 2/0

1. In an automatic transmission for a vehicle having a speed changinggear unit and frictionally engaging means for accomplishing theselective engagement of the gears in the speed changing gear unit, anautomatic shift control system comprising: a hydraulic actuating circuitincluding a shift valve for distributing the working fluid to saidfrictionally engaging means for controlling said frictionally engagingmeans; means for generating an engine torque responsive signal; meansfor generating a vehicle speed resPonsive signal; a first shift pointcomputing circuit for computing one of said two signals or computing therelation between said two signals; a second shift point computingcircuit having a gradient operating circuit and controlled by a gradientresponsive signal generated by said gradient operating circuit; and acircuit for delivering an electrical output signal in response to theapplication of one of the outputs from said two computing circuits so asto actuate said shift valve.
 2. In an automatic transmission for avehicle having a speed changing gear unit and frictionally engagingmeans for accomplishing the selective meshing engagement of the gears inthe speed changing gear unit, an automatic shift control systemcomprising: a hydraulic actuating circuit including a manual valve and ashift valve for distributing the working fluid to said frictionallyengaging means for controlling said frictionally engaging means; meansfor generating an engine torque responsive signal; means for generatinga vehicle speed responsive signal; a first shift point computing circuitfor generating a signal when the relation between said two signalssatisfies a predetermined condition; a second shift point computingcircuit including a gradient operating circuit for generating a signalwhen said engine torque responsive signal, said vehicle speed responsivesignal and the rate of variation of said vehicle speed responsive signalsatisfy predetermined conditions, an operating circuit for generating asignal when said engine torque responsive signal and said vehicle speedresponsive signal satisfy other predetermined conditions, and a bistablememory circuit for continuously generating an output signal in responseto the application of an input signal to one of input terminals thereofand continuously inhibiting the delivery of the output signal inresponse to the application of an input signal to the other inputterminal thereof so that the output signal can be continuously deliveredfrom said bistable memory circuit in response to the application of theoutput signal from said gradient operating circuit to one of said inputterminals of said bistable memory circuit and the delivery of the outputsignal from said bistable memory circuit is continuously inhibited whenthe output signal from said operating circuit is applied to the otherinput terminal of said bistable memory circuit; and an OR circuit fordelivering an output signal when one of the output signals from saidfirst and second shift point computing circuits is applied thereto so asto actuate said shift valve.
 3. In an automatic transmission for avehicle having a speed changing gear unit, frictionally engaging meansfor accomplishing the selective engagement of the gears of said speedchanging gear unit, and control means connected operatively to saidfrictionally engaging means for actuating said frictionally engagingmeans, an automatic shift control system comprising: a manual valvehaving a first position for establishing a relatively high forwarddriving ratio and a second position for establishing a relatively lowforward driving ratio; a shift valve disposed in a communication passagebetween said shift region setting valve and said frictionally engagingmeans for selectively actuating said frictionally engaging means;biasing means engaging one end of said shift valve for biasing saidshift valve in a direction giving the high forward driving ratio;solenoid means engaging the other end of said shift valve for urgingsaid shift valve in the other direction giving the low forward drivingratio in response to the supply of current thereto; shift signal controlmeans determining the supply of the current and the interruption of thecurrent supplied to said solenoid means depending on the runningconditions of the vehicle so as to vary the said shift valve in thecorresponding direction; and switch means disconnectably connecting anelectrical power source with said shift signal control means so that, inthe closed posItion of said switch means in the first position of saidmanual valve, said shift signal control means actuates said shift valveto give the high forward driving ratio as well as the low forwarddriving ratio, while in the open position of said switch means, saidshift signal control means is unable to carry out its control operationand said biasing means for said shift valve solely gives the highforward driving ratio.
 4. In an automatic transmission for a vehiclehaving a throttle controlled engine, a driven member, a fluid pressuresource connected to and driven by said engine, gear means having gearelements which define plural torque delivery paths between said engineand said driven member, and fluid pressure operated servos forcontrolling relative motion of the gear elements of said gear means tochange a gear ratio, an automatic shift control system comprising:hydraulic actuating circuits for interconnecting said servos and saidpressure source including shift valve means for selectively distributingfluid pressure from said source to said servos so as to change a gearratio; solenoid means for operating said shift valve means; a source ofvoltage; means for generating a vehicle speed responsive signal; meansfor generating a throttle position responsive signal; a first shiftpoint computing circuit including a differential amplifier for comparingsaid vehicle speed responsive signal and said throttle positionresponsive signal with each other and generating an output signal whenthe relation between said both signals satisfies a predeterminedcondition; a second shift point computing circuit including an operatingcircuit, a gradient operating circuit and a bistable memory circuit,said operating circuit setting said vehicle speed responsive signal andsaid throttle position responsive signal therein and generating anoutput signal when said signals satisfy a predetermined condition, saidgradient operating circuit having a circuit for differentiating saidvehicle speed responsive signal to compute an acceleration of thevehicle, setting said throttle position responsive signal, said vehiclespeed responsive signal and a vehicle acceleration signal therein andgenerating an output signal when said signals satisfy a predeterminedcondition, and said bistable memory circuit being connected to receivethe output signals of said operating circuit and said gradient operatingcircuit to establish a stable on-off state of output according to thestates of said input signals; and an OR circuit connected to receive theoutput signals of said differential amplifier and said bistable memorycircuit for generating an output signal of a logical sum of said inputsignals, the output of said OR circuit controlling energization of saidsolenoid means, whereby a gear ratio is changed according to the drivenshaft responsive signal, the throttle position responsive signal and anacceleration of the vehicle.
 5. An automatic shift control system asdefined in claim 4, wherein said operating circuit comprises: a firstthrottle position setting operating circuit including reference voltagemeans connected to receive the throttle position responsive signal froma variable resistor and to conduct when the level of said signal exceedsthat of the reference voltage; a first driven shaft speed settingoperating circuit including reference voltage means connected to receivethe driven shaft speed responsive signal from a frequency-DC voltageconversion circuit and to conduct when the level of said signal exceedsthat of the reference voltage; and a first AND circuit connected toreceive the output signals of said first throttle position settingoperating circuit and said first driven shaft speed setting operatingcircuit for giving a logical product of said both input signals.
 6. Anautomatic shift control system as defined in claim 4, wherein saidgradient operating circuit comprises: a second throttle position settingoperating circuit including reference voltage means coNnected to receivethe throttle position responsive signal from a variable resistor and toconduct when the level of said signal exceeds that of the referencevoltage; a second driven shaft speed setting operating circuit includingreference voltage means connected to receive the driven shaft speedresponsive signal and to conduct when the level of said signal exceedsthat of the reference voltage; a low-pass filter connected to receivethe driven shaft speed responsive signal for absorbing high frequencycomponents of said speed signal; a differentiator connected with anoutput of said low-pass filter for differentiating the driven shaftspeed responsive signal having an improved waveform, the output signalof said differentiator representing a differentiated value of the speedresponsive signal or a signal representative of the vehicleacceleration; an acceleration setting operating circuit includingreference voltage means and adapted to be energized when theacceleration signal exceeds a reference voltage; a delay circuit forreceiving the output signal of said acceleration setting operatingcircuit and generating an output signal when the duration of the inputsignal is longer than a predetermined period of time; and a second ANDcircuit connected to receive the output signals of said second throttleposition setting operating circuit, said second driven shaft speedsetting operating circuit and said delay circuit for giving a logicalproduct of said input signals.
 7. In an automatic transmission for avehicle having a throttle controlled engine, a driven member, a fluidpressure source connected to and driven by said engine, gear meanshaving gear elements which define plural torque delivery paths betweensaid engine and said driven member, and fluid pressure operated servosfor controlling relative motion of the gear elements of said gear meansto change a gear ratio, an automatic shift control system comprising:hydraulic actuating circuits for interconnecting said servos and saidpressure source including shift valve means for selective distributingfluid pressure from said source to said servos so as to change a gearratio; solenoid means for operating said shift valve means; a source ofvoltage; a variable resistor cooperating with a throttle valve toprovide a voltage which varies with changes of the throttle position; atachogenerator connected to a dirven shaft for producing an AC voltagewhich varies with the speed of the driven shaft; a frequency DC voltageconversion circuit connected to the tachogenerator for converting the ACvoltage into a DC voltage so as to develop a signal voltage proportionalto the speed of the driven shaft; a potentiometer for modifying thesignal voltage proportional to the speed of the driven shaft; switchingcontacts arranged to be operated by a switching relay for alternatelyconnecting one of the frequency-DC voltage conversion circuit and thepotentiometer; a differential amplifier connected to receive a throttleposition responsive signal from said variable resistor and a drivenshaft speed responsive signal from said switching contacts for comparingthe throttle position responsive signal with the driven shaft speedresponsive signal, said switching relay being connected to an outputlead of said differential amplifier; a first throttle position settingoperating circuit including reference voltage means connected to receivethe throttle position responsive signal from said variable resistor andto conduct when the level of said signal exceeds that of the referencevoltage; a first driven shaft speed setting operating circuit includingreference voltage means connected to receive the driven shaft speedresponsive signal from said frequency-DC voltage conversion circuit andto conduct when the level of said signal exceeds that of the referencevoltage; a first AND circuit connected to receive the output signals ofsaid first throttle position setting operating circuit and said firstdriven shaft speed setting operAting circuit for giving a logicalproduct of said both input signals; a second driven shaft speed settingoperating circuit including reference voltage means connected to receivethe driven shaft speed responsive signal and to conduct when the levelof said signal exceeds that of the reference voltage; a low-pass filterconnected to receive the drive shaft speed responsive signal forabsorbing high frequency components of the driven shaft speed responsivesignal; a differentiator connected with an output of said low-passfilter for differentiating the driven shaft speed responsive signalhaving an improved waveform, the output of said differentiatorrepresenting a differentiated value of the driven shaft speed responsivesignal or a signal representative of the vehicle acceleration; anacceleration setting operating circuit including reference voltage meansand adapted to be energized when the acceleration signal exceeds thereference voltage; a delay circuit for receiving the output signal ofsaid acceleration setting operating circuit and generating an outputsignal when the duration of the input signal is longer than apredetermined period of time; a second AND circuit connected to receivethe output signals of said second throttle position setting operatingcircuit, said second driven shaft speed setting operating circuit andsaid delay circuit for giving a logical product of said input signals; abistable memory circuit connected to receive the output signals of thefirst AND circuit and the second AND circuit for establishing a stableon-off state of output according to the states of said input signals;and an OR circuit connected to receive the output signals of saiddifferential amplifier and said bistable memory circuit for giving alogical sum of said both input signals, the output of said OR circuitcontrolling energization of said solenoid means, whereby a gear ratio ischanged according to a change of an output siganl resulting fromcomparison between the driven shaft speed responsive signal and thethrottle position responsive signal and also according to a change of anoutput signal resulting from comparison between a differentiated valueof the driven shaft speed responsive signal, or a vehicle acceleration,and a reference vehicle acceleration.
 8. In an automatic transmissionfor a vehicle having a throttle controlled engine, a driven member, afluid pressure source connected to and driven by said engine, gear meanshaving gear elements which define plural torque delivery paths betweensaid engine and said driven emmber, and fluid pressure operated servosfor controlling relative motion of the gear elements of said gear meansto change a gear ratio, an automatic shift control system comprising:hydraulic actuating circuits for interconnecting said servos and saidpressure source including a manual valve having a first position forestablishing a relatively high forward speed ratio and a second positionfor establishing a relatively low forward speed ratio, a shift valvedisposed in a communication passage between said manual valve and saidservos for selectively supplying fluid pressure to said servos to changea gear ratio, spring means for biasing said shift valve in a directionestablishing the high forward speed ratio, and solenoid means for urgingsaid shift valve in the other direction establishing the low foraardspeed ratio by overcoming the biasing force of said spring means whensaid manual shift valve is in said first position, said shift valvebeing biased by said spring means in the direction to establish the lowforward speed ratio when said manual valve is in second position; asource of voltage; shift signal control circuits including means forgenerating a throttle position responsive signal voltage, means forgenerating a vehicle speed responsive signal voltage, a differentialamplifier connected to receive the throttle position responsive signalvoltage and to receive the vehicle speed responsive signal voltage forcomparing said boTh signal voltages to generate an output signal byturning conductive when the throttle position responsive signal voltageis higher than the vehicle speed responsive signal voltage, and anamplifier for amplifying the output signal of said differentialamplifier to energize solenoid means; and switch means disconnectablyconnecting said source of voltage with said shift signal controlcircuits, whereby when said switch means is in a closed position, thefirst position of said manual valve establishes the low forward speedratio upon energization of said solenoid means by said shift signalcontrol circuit and establishes the high forward speed ratio upondeenergization of the same, while when said switch means is in an openposition, said shift signal control circuits do not operate and saidsolenoid means is in a deenergized state, whereas the first position ofsaid manual valve establishes the high forward dpseed ratio and thesecond position thereof establishes the low forward speed ratio.
 9. Animproved shift control for use in a vehicle having an engine andautomatic transmission including a gear change unit capable of beingselectively established in any one of a plurality of forward drivinggear ratios, including at least respective lower and higher speed gearratios, when shifted thereinto, said shift control comprising: loadindicating means responsive to operational load characteristics of saidvehicle for producing outputs indicative of variations of said loadcharacteristics; first shift point computing means responsively coupledto said load indicating means for operative coupling to said gear changeunit to establish a change from said lower to higher gear ratio whensaid output indicates a certain load characteristic; and second shiftpoint computing means including a gradient operating circuitresponsively coupled to said load indicating means for operativecoupling to said gear change unit to establish a change from said higherto lower gear ratio when an output thereof indicates a certain loadcharacteristic co-relative to a gradient exceeding a selected amount.10. A shift control system as in claim 9, wherein said load indicatingmeans includes: vehicle speed and engine load responsive means; andmeans for coupling said responsive means to said vehicle for producingrespective outputs indicative of vehicle speed and engine load.
 11. Animproved shift control system for use in a vehicle having an engine andautomatic transmission including a gear change unit capable of beingselectively established in any one of a plurality of forward drivinggear ratios, including at least respective lower and higher speed gearratios, when shifted thereinto, said shift control system comprising:automatic transmission shifting means for automatically shifting saidtransmission from one to another of said driving gear ratios based uponcertain vehicle conditions; gradient responsive means for producing agiven electrical output signal indicative of gradients exceeding aselected amount in accordance with operational load characteristics ofthe vehicle correlative to gradient; and means operatively coupled tosaid gradient responsive means and said automatic shifting means forcausing said transmission, when it has been automatically shifted intosaid higher gear ratio by said shifting means, to be automaticallyshifted down from said higher to said lower gear ratio when said givenelectrical output occurs due to said selected amount of gradient beingexceeded.
 12. An improved electrical shift control system for use in avehicle of the type driven by an engine having an automatic transmissionsystem including a speed change gear unit coupled to said transmissionfor selectively accomplishing shifting said speed change gear unit asbetween a plurality of gear ratios including at least lower and highergear ratios, and a hydrauilc actuation circuit for controlling saidspeed change gear unit including distributor valVe means for selectivelydistributing a source of actuating fluid under pressure thereto, and anelectrical shift control system for controlling the operation of saiddistributor valve means and hence the shift as between said gear ratios,said improved electrical shift control system comprising: vehicleresponsive means including engine load responsive means and vehiclespeed responsive means for producing output signals indicative of therespective conditions of said load and speed responsive means; firstshift point computing means responsively coupled to said vehicleresponsive means for producing selected outputs in response to theoccurrence of respective relationships of said output signals forselectively activating said distributor valve means for shifting saidgear unit as between said higher and lower ratios in accordance withsaid respective output signals; second shift point computing meansresponsively coupled to the vehicle responsive means and including agradient operating circuit for producing an output indicative ofgradients exceeding a selected amount in accordance with operationalload characteristics of the vehicle correlative to said gradient; andmeans including circuit means responsively coupled to said gradientcircuit for operatively controlling said distributor valve means inaccordance with said gradient circuit output thereby modifying theshifting of said vehicle upon the encounter of gradients exceeding theselected amount.
 13. An improved shift control system as in claim 12,wherein said circuit means is coupled to said first shift pointcomputing means output and the output of said gradient circuit fordelivering respective signals to said distributor valve means andcomprises: bistable memory means, having two stable states, andresponsively coupled to said gradient circuit for producing an output inone of its stable states in response to the output thereof indicative ofthe gradient exceeding the selected amount for activating saiddistributor valve, and producing no output in its other stable state inresponse to the gradient circuit output indicative of the gradient lessthan the minimum amount, and OR circuit means responsive to saidbistable means and said first shift point computing means for activatingsaid distributor valve to effect shifting of said gear unit inaccordance with the presence or absence of an output of said OR means.14. An improved shift control system as in claim 12 wherein said engineis throttle controlled and said load responsive means includes: meansresponsive to the degree of actuation of said throttle for establishinga signal indicative thereof.
 15. An improved shift control system as inclaim 12, wherein said vehicle speed responsive means includes: agenerator coupled to the outout of the transmission and driven therebyfor producing a variable output in accordance with the rotational speedthereof, indicative of vehicle speed.
 16. An improved shift controlsystem as in claim 12, for use with the said transmission system whenthe gear unit is shiftable between at least low, medium, and high gearratios, the latter two being said lower and higher ratios, and saiddistributor valve means includes first and second distributor valves,said shift control system further including a third shift pointcomputing means responsively coupled to said vehicle responsive meansfor providing outputs to control said first distributor valve, thecombined outputs of said first and second shift point computing meansbeing operable to control said second distributing valve.
 17. Animproved shift control system as in claim 16 wherein said second shiftpoint computing circuit means further includes: second means responsiveto the vehicle responsive means for producing selected outputs inresponse to the occurrence of respective different relationships thereoffor effecting gear engagements different from those provided by saidfirst distributor valve.
 18. An improved shift controL system as inclaim 17 further including: bistable circuit means having two stablestates and responsively coupled to said gradient circuit for producingan output in one of its stable states in response to the output thereofindicative of the gradient exceeding said selected amount for activatingsaid second distributor valve and producing no output in its other statein response to the gradient circuit output indicative of less than theselected amount, and OR circuit means responsive to said bistable meansand said second shift point computing means for activating said seconddistributor valve to effect shifting of said gear unit in accordancewith the presence or absence of an output of said OR means.
 19. Animproved shift control system as in claim 12, wherein said gradientresponse operating circuit includes: means responsively coupled to saidvehicle responsive means for producing a first output upon theoccurrence of a vehicle speed less than a selected minimum, an engineload greater than a selected maximum, said output being indicative of aroad inclination greater than a selected degree and for furtherproducing a second output in response to a respective engine load andvehicle speed respectively less than and greater than selected amountsfor indicating level road conditions.
 20. An improved shift controlsystem as in claim 19 wherein said engine is throttle controlled andsaid load responsive means includes: means responsive to the degree ofactuation of said throttle for establishing a signal indicative thereofand accelerometer means responsive to said speed responsive means forproducing an output indicative of vehicle acceleration.
 21. An improvedshift control system as in claim 20 wherein said gradient responsiveoperating circuit means includes: first AND circuit means responsive toselected outputs of said vehicle responsive means including the vehiclespeed response means, the accelerometer means, and the throttleresponsive means, for producing an output for activating said bistablemeans to its first condition, and second AND circuit means responsive toselected outputs of said vehicle response means including the vehiclespeed and throttle responsive means for activating said bistable meansto its second condition.
 22. An improved shift control system as inclaim 21 further including OR circuit means coupled to said bistablemeans output and the second shift point computing means for producing anoutput when either of said means is producing its selected output foractivating said distributor valve means.
 23. An improved shift controlsystem as in claim 20 wherein said first and second shift pointcomputing means each include: shift point operating means responsive tosaid vehicle responsive means including the throttle degree responsivemeans and the vehicle speed detector for delivering an output inresponse to selected relationships of the signals therefrom.
 24. Animproved shift control system as in claim 23, wherein said shift pointcomputing means each further include: means responsively coupled to saidvehicle speed detector output, for providing a modulated versionthereof, selection means for controlling the input of said shift pointcomputing means for coupling the modulated version of said vehicle speedoutput thereto in response to the output of said shift point operatingmeans, said modulated version of said vehicle speed output beingattenuated so as to provide hystersis to said shift point computingmeans.
 25. An improved shift control system as in claim 24, whereinshift point computing circuit includes a comparator for sensing therelative magntidues of the throttle position detector output and thevehicle speed detector output and producing its output in accordancewith a preset relation.
 26. an improved shift control system as in claim12 further including a manual shift valve for distributing said fluid;and switch means for coupling an electrical power source to said controlmeans, operAtively coupled to said shift valve for rendering saidelectrical control system inoperative to effect said automatic shiftingof said gear unit when said manual shift valve is moved from anautomatic to a manual mode.